The invention relates to a tube for a peristaltic pump.
Specifically, though not exclusively, the invention can be usefully employed for transport of a liquid, for example a corporeal fluid (blood) and/or a medical fluid, in a medical apparatus, in particular in an apparatus for extracorporeal blood treatment, such as for example a dialysis apparatus.
The use of deformable-tube peristaltic pumps for transport of liquids is known and widespread. Some examples of deformable tubes used in peristaltic pumps are shown in patent publications U.S. Pat. No. 4,080,113, WO 89/04923, WO 95/11383, U.S. Pat. No. 5,088,522, EP 0 388 596, U.S. Pat. No. 5,242,279. In a peristaltic pump the tube, which is elastically deformable and contains the fluid to be transported, is squeezed by a mobile device (for example a rotor having at a periphery thereof two or more squeezing rollers) in a zone which progressively advances along the length of the tube so as to push the fluid forward. The tube has elastic return which enables the squeezing-pushing action to be repeated cyclically.
One of the problems of known-type peristaltic pumps consists in the fact that the deformable tube, generally made of a relatively soft plastic material, such as for example plasticated PVC, is prone to considerable wear by effect of the squeezing and sliding pressure it is subjected to by the mobile device, with a consequent degrading of its characteristics, especially its mechanical characteristics, for example its elastic return capacity. This has a considerable effect on the efficiency of the peristaltic pump over a long use time, causing the fluid flow along the tube to diminish progressively even where the squeezing-pushing action stays the same.
This leads to various drawbacks.
Firstly, the progressive drop in performance of the peristaltic pump considerably limits the work time of the deformable tube. In applications where it is possible to do so, the worn deformable tube is periodically replaced. In other applications, for example in extracorporeal blood circuits, in which the deformable tube (also known as the pump segment) cannot be easily substituted in isolation from the rest of the circuit; the whole circuit has to be changed too, with consequent complications and a considerable impact on costs.
Secondly, the variability over time of the peristaltic pump efficiency leads to a certain imprecision in the determination of the fluid flow, with a consequent need, in some cases, to set up elaborate flow control and regulation systems, especially in applications where the precision of the flow measure is essential, such as for example in medical apparatus in general, and in dialysis apparatus in particular, where control of the ultrafiltration flow and/or the infusion flow must be very precisely performed.